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Vintage RC Helicopters - Lite Machines
LMH 100 (1994) LM brought out an unusual helicopter in 1994 called the LM-100. Though four function it was powered by a small Cox 0.51 size engine which had very little in the way of silencing so was quite noisy for such a small helicopter. It was fixed pitch with plastic flapping blades but the most unusual feature was the gyro stabilised tail rotor. This was called the Arlton Gyro and had a small stabilizing rotor controlling the pitch of the tail rotor in a similar way to the flybar controlling the main rotor. As a historic note this was a similar system to that used in the early models of John Burkam (Super Suzie) and Gene Rock (S.S.P.). As the engine was specific to the helicopter and buyers would have been unlikely to have one already, the majority of sales were for the 'combo' version that included everything but the radio gear.
Full specifications
Technical Bulletin 01 - Feb 1995 - Cox Globee glow plug maintenance. Technical Bulletin 02 - Mar 1995 - Effect of low battery voltage on glow plug. Technical Bulletin 03 - Jul 1995 - Effects of pitch of main blades on performance. Technical Bulletin 04 - May 1996 - effect of CA glue on canopy material. Historic review of the initial helicopter development by Paul Arlton. A couple of buyer reviews from 1997 - review A - review B, plus a few more - review C - review D - review E. LMH 110 (1998)
In 1998 the model was updated to the LMH-110 and the Cox 0.51 was replaced with the Norvel Vmax-6 of capacity 0.61 CU, this engine was similarly controlled by a rotary valve in the exhaust system but this time it also incorporated a silencer and thus was much quieter that the 100 model. The following is the introduction from the 1999 version manual; note that the first line is, of course, not true by a long way though the first made in the USA...!!! The Lite Machines Model 110 helicopter is the first mass-produced radio controlled micro helicopter in the world. It is intended as an introductory helicopter for those modellers intrigued by helicopters and helicopter flight, but unable to justify the significant investment in time and money required for traditional helicopter models. The Model 110 can withstand tipping over and minor crashes with little or no damage. Many flight skills such as basic hovering, nose-in hovering, low speed manoeuvring, forward and backward flight, and pirouettes can be mastered without busting the family budget with a larger, more complex machine. The Model 110 utilizes advanced aerodynamics that enable it to fly on 1/10th of a horsepower which is roughly the power consumed by a 75 watt light bulb. In comparison, .30 to .60 size model helicopters use one to two horsepower (10 to 20 times more). The fixed-pitch main rotor of the Model 110 helicopter combines Sub-rotor technology and free-flapping, foldable rotor blades in a rugged, high lift rotor system with fewer than half the number of parts found in collective-pitch helicopters. Main rotor lift is controlled by changing the rotational speed of the main rotor rather than varying the pitch of the individual rotor blades (such as with “collective-pitch” type main rotor systems). Fixed-pitch main rotors are substantially simpler than collective-pitch systems and are ideal for beginners. Collective-pitch main rotors allow for advanced aerobatics and engine-off autorotation manoeuvres that are typically flown by more experienced pilots. The tail rotor mechanism of the Model 110 helicopter incorporates a light-weight Arlton Gyro stabilizer which eliminates the need for an expensive electronic gyro and extra capacity receiver batteries. The unique central keel fuselage structure is simple, strong and easy to assemble and repair - a far cry from the fragile construction of many electric helicopters. Designed on modern computer-aided design (CAD) systems and computer-aided manufacturing (CAM) systems, the structure of the Model 110 helicopter incorporates eight types of engineering plastics, four aluminium alloys, several high strength steels, aircraft plywood and multiple protective surface coatings. As noted a new engine was supplied in order to give more performance and better noise control which had been a major problem for the original machine as it could only be operated well away from other people; it was also better for the pilot to wear ear plugs to prevent serious ringing in the ears!!!! Additionally, the open exhaust resulted in fuel residue permeating throughout the whole model thus making it difficult to keep clean; the following is the engine introduction. The Norvel Vmax-6 helicopter engine takes the model 110 where you want it to go, on inexpensive 15 % nitro fuel. The special venturi and directional intake ports on this .06 cu. in.(1cc) Schnuerle-ported powerhouse are tuned for easier starting and extra lugging power. The rugged Vmax-6 crankshaft is supported by a durable bronze bushing for long life at maximum power. The unique Vmax-6 throttle/muffler includes a tapered slide-valve throttle for more precise linear throttle control. Engine exhaust is directed downward to keep your Model 110 clean and quiet.
LMH-110 Exploded views - 1998 version Technical Bulletin 06 - May 1998 - Engine problems due to fuel contamination. Technical Bulletin 07 - May 1998 - Effect of needle valve damage. Technical Bulletin 08 - Mar 1998 - Recommended fuels for the Norvel engine. LMH-110 Construction manual - 1999 version and of very high quality and very comprehensive. LMH Operators guide - 2001 version and supplements the build manual. LMH-110 Parts list - 1999 full parts list with prices and model exploded views. Technical Bulletin 09 - Jul 2000 - Effect of fuel line vibration on engine tuning.
The engine was upgraded to the Vmax-6B which had the same capacity but better specification and a revised head/sealing ring configuration. LMH 116 (2002) The basic version retaining the Arlton gyro was slightly revised and renamed the 116, designated as 'Simple' gas power and was made available in the following options;
Technical Bulletin 11 - Feb 2002 - Spherical cylinder seals and Vmax engines (models 6B and 7). LMH 117 (2002)
As per the Corona below, given the performance increase in gyros the 110 was made available without the Arlton gyro and also with the upgraded larger Norvel Vmax-7 engine of 0.76 cu capacity, revised 2001 specification as noted below;
This was marketed as the 'Quiet' gas power model given that the original Vmax 6 engine was noisy and the Vmax 7 was a much quieter engine. Same options as the model 116 above but all without any gyro. Technical Bulletin 11 - Feb 2002 - Spherical cylinder seals and Vmax engines (models 6B and 7). LMH 120A Corona (2001)
In 2001 Light Machines brought out a revised model, the Corona 120A, being a 110 fundamentally redesigned for electric power. The basic layout remained along with the main drive train however, the main frame was redesigned to remove the fuel tank, replace the engine with the electric motor and provide securing for a flight battery. Whilst electric models were gaining in popularity, they all had the same problem of low relative power to the same weight glow engine and also heavy battery weight for a reasonable flight endurance. To help counter these deficits the Arlton Gyro was removed as low weight piezo gyro's of a reasonable price were available and bigger main blades were fitted to give more lift and reduce the rotor disc loading; a longer tail boom was then required to give clearance for the tail rotor.
Revised Corona specifications
As can be seen from the specifications, the weight had increased dramatically by 60% from the 110 models however, with the longer blades the disc area had also increased by 55% and thus the overall disc loading remained near enough the same. The result being that rotor characteristics remained very similar to its predecessor and so did flying characteristics with the overall weight increase making the model more stable and better able to cope with turbulence. The model was marketed with two options; 1) Basic Combo Kit - 120 Helicopter, Electro-Fusion 7 motor and Electro-Fusion accessories pack. 2) Standard Combo Kit - As the basic kit plus Electro-Fusion 35 Speed Controller and standard accessory pack. Most bought the Standard kit as it included the matched ESC for the motor and both kits additionally required full radio plus gyro and battery pack of choice; the Basic Combo was bought if the intention was to fit a brushless motor from the start. The motor provided was not considered the best available and reports of 'dying' after only 5-10 flights were common. One reason for this lack of longevity was that brushed motors required careful 'running in' which was not always appreciated. Without this care the motor /commutator contact was damaged causing lots of 'sparking' and high resistance so the motor efficiency drastically reduced and power dropped sharply. Higher quality motors such as the Kyosho Atomic Force were recommended as these motors generally did not require the same level of running in and also provided more power. The speed controller provided with the kit was a relabelled Castle Creations Pegasus 35 (Set-up manual here) which had a reputation for poor 'arming' however, this was due to the arming set point being very close to a transmitter zero stick position and so the cure was to either extend the throw slightly for minimum stick or move the trim point down; problem solved...!!! Another problem arose concerning the increased incidences of tail boom strikes; because the blades were flexible and now much longer if touch down occurred with some back stick held on; the boom could be caught. Obviously the trick is not to do that but it could be prevented by fitting a 'rotor deflector'; this was a flat piece of wood or aluminium about 50mm long secured to the tail boom in the area where the tip would strike and angled down by 10mm towards the direction the rotor would strike. If the blade then tried to go below the edge of the boom this 'ramp' deflected the blade upwards thereby preventing a strike and generally not causing any damage. The tail gearbox was also not as strong as the previous model 110 and tail blade strikes could damage teeth. Unfortunately the flexibility of the legs which were designed to absorb 'heavy' landings without damage tended to cause the blades to touch down so fitting a more substantial tail support helped prevent contact under these circumstances. It was also found that it was better to use two of the four dot blade grips which reduced the blade incidence from that recommended in the manual as this requiring higher revs for the same lift thus giving quicker head response. This was especially so when higher performance motors were used as the lower head speed of the standard setting did not allow them to perform efficiently. LMH-120A Construction manual - 2001 Corona version LMH Operators guide - 2001 version and supplements the build manual. Technical Bulletin 10 - Dec 2001 - Additional info for Fusion 35 speed control and mounting of motor. http://www.rcgroups.com/forums/showthread.php?t=185388 - Excellent 'Forum' build article with lots of photo's plus detailed Corona build. As technology improved the standard brushed motors were replaced with brushless types of lower weight and significantly more power thus enabling better performance and the introduction of Li-Po type batteries allowed for either decreased flying weight of more often than not for the same weight an much extended duration.
LMH Corona (2008)
Light machines begin redevelopment of the Corona and it was intended to bring it fully up to date for direct drive by a brushless motor. However, this was not followed through and it was decided to sell the development to Multiplex of Germany who finalised the design and encased it in an 'Elopor' body thus making it a really 'tough' little machine. So, in the guise of the Multiplex 'funcopter' the 'Corona' lived on.
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